Heat sink

ABSTRACT

A heat sink is manufactured by forming a fin  2  for dissipating heat by separating a length of material from a substrate  1  while leaving the proximal end attached to the substrate  1 . The fins are cut from the substrate by stamping process using the stamping single or progressive die tooling cutting the substrate  1  along dotted line  16 . The heat sink is a unitary construction, with the fins  2  being integrally formed with the substrate  1.

BACKGROUND TO THE INVENTION

[0001] The present invention relates to heat sinks and to a method offorming the same. More particularly, but not exclusively, the presentinvention relates to an improved method of forming heat dissipating finsof a heat sink.

[0002] Heat sinks are well known components used, for example, fordissipating heat from electronic circuitry, CPUs (computers) andmicroprocessors in order to cool the components to enable them tofunction consistently and properly. Heat sinks are often used inconjunction with printed circuit boards which are found in electronicequipment such as television sets and audio amplifiers. There are manytypes of conventional heat sinks.

[0003] One of the most widely used heat sink is extruded heat sink. Itis well know to manufacture the extruded heat sink by extrudingaluminium, through a complex shaped die to produce a section. Extrusionlimits, such as the fin height-to-gap and fin thickness, usually dictatethe flexibility in design options. Typically fin height-to-gap aspectratio of up to 6 and minimum fin thickness of 1.3 mm, are attainablewith a standard extrusion. A 10 to 1 aspect ratio and a fin thickness of0.8 mm can only be achieved with special die design features. However,as the aspect ratio increases, the extrusion tolerance is compromised.Also, extrusion equipment is expensive, the process slow, Further, inorder that it can be made by an extrusion process, a heat sink must bemade from aluminium, and other materials cannot be used.

[0004] Another conventional type or heat sink is folder type heat sinkthat consists of a base to which a continuous corrugated fin sheet isattached A plurality of corrugations are formed, which are elongate,adjacent corrugations having the appearance of oppositely facing slots.To attach the corrugated sheet to the base portion, square slots areformed in the corrugation. The corrugated sheet is then slotted in tothe base which is extruded so as to have square cross section ridgeswhich are inserted into the slot holes. To ends of the ridges are thenstamped flat to hold the corrugated sheet on to the extruded base. Thecorrugations thus form fins of the heat sink. One disadvantage of suchan arrangement is that the corrugated sheet which forms the fins forms aheat trap between alternate pairs of fins.

[0005] In another type of conventional heat sink the fins are formedfrom a numbers of separate sheets of material which are pressed to forma U-shaped fin. The fins are then riveted to an extruded aluminium baseor sheet metal piece using two or more rivets. Such an arrangement isdisadvantageous in that the additional manufacturing step of applyingthe rivets is necessary, and further in that the rivets may work lose,reducing the effectiveness of the heat sink.

SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide a heat sinkwhich provides improved heat dissipation.

[0007] It is another object of the present invention to provide animproved method of forming the fins to achieve maximum fin height-to-gapaspect ratio and to reduce the fin thickness to as thin as 0.2 mm. Theimproved method is less expensive, faster and more flexible, and whichresults in higher cooling capacity and more reliable heat sinks.

[0008] According to a first aspect of the present invention, there isprovided a method of forming a heat sink, including forming a fin fordissipating heat by separating a thin length of material from asubstrate while leaving the proximal end attached to the substrate.

[0009] Such a method may allow a heat sink to be formed from a unitarysheet of material. The fins are an integral part of the substrate andtherefore do not need to be attached to a base (As the folder type orU-fin heat sink does), so there are no joints which could reduceconduction of heat or deteriorate with rough handling and/or ageing.Fins may be produced by cutting thin lengths of material from thesubstrate.

[0010] The fin may be arcuate in configuration.

[0011] The fin may extend generally perpendicularly to the plane of thesubstrate. This may be advantageous as it allows heat to escape from aplurality of fins as it rises between the fins.

[0012] A ridge may be formed in the surface of the substrate as a resultof the cutting process to form the fin. The ridge may form the distalend of the fin.

[0013] The fin may be formed by the stamping process using the singledie tooling or a progressive die tooling.

[0014] The method may typically be used to form a plurality of the veryfine fins up to 0.2 mm in thickness on the substrate. A plurality offine fins that provide larger surface area expose to the air stream willprovide improved heat dissipation.

[0015] The plurality of fins may be formed in a series of spaced apartrows. The space between the adjacent fins can be minimised to achievethe maximum fin height-to-gap aspect ratio (20 to 40) thus increase thesurface area for better cooling capacity. The spacing apart of the rowsmay allow improved air circulation, which may also increase heatdissipation.

[0016] According to a second aspect of the present invention there isprovided a heat sink having a substrate and a plurality of fins fordissipating heat integrally formed therewith. By forming the finsintegrally with the heat sink main body, a unitary structure is formed.

[0017] Each fin may be a single thin layer of material extending fromthe substrate. By forming the fins as single layers, no heat is trappedwithin a single fin, and heat dissipation may be improved.

[0018] The heat sink may comprise aluminium or copper, and may consistof only one of aluminium and copper. With prior art extruded heat sinks,only aluminium could be used.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] For a better understanding of the present invention, embodimentswill now be described by way of example, with reference to theaccompanying drawings, in which:

[0020]FIG. 1 shows a perspective view of a fully formed heat sink inaccordance with the present invention;

[0021]FIG. 2 shows a side plan view of a heat sink during manufacturethereof;

[0022]FIG. 3 shows an overhead plan view of the heat sink of FIG. 1;

[0023]FIG. 4 shows a side elevational view of the heat sink of FIG. 1 incompleted form;

[0024]FIG. 5 shows a front elevational view of the heat sink of FIG. 1in completed form;

[0025]FIG. 6 shows a cross section taken along the line A-A of FIG. 3;

[0026]FIG. 7 shows a front elevational view of a heat sink according toa second embodiment of the present invention;

[0027]FIG. 8 shows a front elevational view of a heat sink according toa third embodiment of the present invention;

[0028]FIG. 9 shows a front elevational view of a heat sink according toa fourth embodiment of the present invention; and

[0029]FIG. 10 shows a side elevational view of the heat sink of FIG. 9.

DESCRIPTION OF THE EMBODIMENTS

[0030] Throughout the drawings, the same reference numerals aregenerally used to designate like elements.

[0031] FIGS. 1 to 6 show a first embodiment of the present invention.The heat sink comprises a base or substrate 1, being a block of metalsuch as aluminium or copper. Layers of the substrate 1 are peeled orshaved away successively in order to form heat dissipative fins 2. Thefins 2 may be formed in a series of columns 3 and rows 5. The fins 2 ofeach column 3 may be formed simultaneously. The rows 5 of fins 2 areseparated by a gap 6. Between the rows 5 of fins 2 a rib 8 is present.Between each rib 8 is a groove 10, which is formed as the fins 2 are cutfrom the substrate 1.

[0032] The fins 2 are arcuate. The arc of each fin 2 illustratedrepresents approximately {fraction (1/8)} of a circle. The arc profiledepends on the design of the tool that forms the fins 2, and thethickness and height of the fins 2.

[0033]FIG. 2 shows how a heat sink is formed from substrate 1.Initially, the substrate 1 is a cuboid.

[0034] A cutting tool C of a stamping die tooling engages the substrate1 to form the fin 2 from the substrate 1. The substrate 1 is fed intothe stamping tool C manually or by using a material feeder (not shown).The feeding pitch corresponding to each stroke of the press machine mayvary depending on the requirements of the tooling as well as therequired thickness of the fins, fin height and pitch between the fins ofthe heatsink

[0035] To facilitate the shaving/peeling process to form the fins 2 atthe initial stage of the shaving process, a series of grooves 12 may becoined/formed on the surface of the substrate 1. The substrate 1 is thenprogressed toward the shaving/peeling portion of the cutting tool. Oncethe shaving and peeling portion of the cutting tool C contacts thesubstrate 1, material will start peeling from the surface of thesubstrate 1. The first few fins will directly peel off from thesubstrate 1 until the proximal end of the fins is able remain connectedto the substrate 1, where the first column of fins is formed. Thesubsequent columns of fins will then be continually formed by thestamping die tool as the substrate 1 is fed forward by a specificdistance on by every stroke of the press machine. These subsequent finswill have a thickness corresponding to the height “h” of the ridge 12.The ridge 12 will form the distal end of the fin 2.

[0036] The shaving/peeling advancement direction A of the cutting tool Cmay vary from approximately 2° to 20° depending on the required finthickness and height as well as the pitch between the fins. The finswill be shaved/peeled along the dotted lines 16 separating a length “L”of substrate material from the main body of the substrate 1 at adistance “l” from the previously formed fins, the distance “l”determining the spacing or pitch between adjacent fins once formed. Theproximal end of the fin 2 remains connected to the main body of thesubstrate 1 after the shaving and peeling process. During the finalphase of movement of the cutting tool C, the fin 2 is peeled away fromthe main body of the substrate 1 so that it lies generally perpendicularthereto.

[0037] This process will create a long strip of substrate 1 with thefins on the surface of the substrate 1. A cutting tool or machine may beengaged later to cut the substrate 1 into small piece with a specificnumber of columns of fins required by the heat sink.

[0038] The pitch 18 between the columns of fins 2 is determined by thedistance l, and is chosen according to the heat dissipation requirementsof the heat sink.

[0039] The gap 6 between the rows 5 of fins 2 is also chosen accordingto the heat dissipation requirements of the heat sink.

[0040] The thickness (corresponding to h) of each fin 2 can also beselected according to the requirements of an individual heat sink.

[0041]FIG. 7 shows a heat sink according to a second embodiment of thepresent invention having only two rows 5′ of fins 2′. The fins 2′ ofeach row 5′ are wider than the fins 2 of the first embodiment.

[0042]FIG. 8 shows a third embodiment of the invention wherein a singlerow 5″ of fins 2″ is formed.

[0043]FIG. 9 shows a fourth embodiment, which is small modification ofthe third embodiment. In the fourth embodiment the fins 2″′ are formedacross the full width of the substrate 1 rather than leaving a rib 8 ateach side, as in the first, second and third embodiments.

[0044]FIG. 10 is a side elevational view of the heat sink of FIG. 9.

[0045] The pitch 18 of the fins 2 according to the embodiments of thepresent invention and the thickness and height of the fins 2 can bevaried within a larger range than is possible using a conventionalprocesses such as extrusion process.

[0046] Also, the process according to the embodiments produces heatsinks faster than the processes of producing an extrusion heat sink,folder type and bonded type heat sink according to the prior art and atlower cost.

[0047] Further, compared with the prior art extrusion process, thebottom surface 14 of the substrate 1 will be relatively flat, improvingheat transmission thereto. Material usage is more efficient by forming aheat sink according to the present embodiments. Heat sinks according tothe present embodiments will be more compact, lighter as less materialis necessary to produce them, compared with prior art heat sinks havingcomparable functionality. The fins can be made thinner than is possiblein the extrusion process. Also, no rivets or other joining means arerequired to connect the fins to the substrate, thereby improving theconductivity of the heat sink and more reliable. The cost is also lowerbecause no additional joining process is needed.

1. A method of forming a heat sink, including forming a fin for dissipating heat by separating a length of material from a substrate while leaving no the proximal end attached to the substrate.
 2. A method according to claim 1, wherein the fin is arcuate or planar.
 3. A method according to claim 1, wherein the fin extends generally perpendicularly to the plane of the substrate.
 4. A method according to claim 1, including forming a ridge in the surface of the substrate for engagement with a cutting tool to form the fin.
 5. A method according to claim 4, wherein the ridge forms the distal end of the fin.
 6. A method according to claim 1, wherein the fin is formed by single or progressive stamping processes by using the single or progressive die tooling.
 7. A method according to claim 1, including forming a plurality of said fins on the substrate.
 8. A method according to claim 7, wherein said plurality of said fins are formed in a series of spaced apart rows. 9-13 canceled 